Name USC loginid e g ttrojan CS 455 Midterm Exam 1 Spring 2012 Bono Feb 16 2012 There are 4 problems on the exam with 45 points total available There are 7 pages to the exam including this one make sure you have all of them There is also a one page code handout that accompanies the exam If you need additional space to write any answers you may use the backs of exam pages just direct us to look there Note if you give multiple answers for a problem we will only grade the first one Avoid this issue by labeling and circling your final answers and crossing out any other answers you changed your mind about though it s fine if you show your work Put your name and USC loginid at the top of the exam Please read over the whole test before beginning Good luck value Problem 1 10 pts Problem 2 10 pts Problem 3 10 pts Problem 4 15 pts TOTAL 45 pts score A Problem 1 10 pts Consider the following program Note more about Point class on code handout public class Prob1 public static void foo Point a a new Point a getX 5 a getY 10 public static void main String args Point p new Point 5 10 Point r p p translate 1 1 foo r System out println p r Part A 6 In the space below draw a box and pointer diagram a k a memory diagram showing all object variables objects and their state as they have changed during the code sequence This includes showing foo s parameter a Part B 2 What is printed by the code For the purpose of this problem assume a Point is printed as follows x y Part C 2 How many Point objects are created by the code above 2 Problem 2 10 pts Implement the class DigitExtractor which breaks up an integer into its individual digits After being initialized with a positive integer each call to nextDigit returns the next digit in the integer starting from the rightmost digit i e a sequence of such calls returns the digits in reverse order Here is an example of code to use the class It extracts all of the digits of 27 054 DigitExtractor extractor new DigitExtractor 27054 while extractor hasNextDigit System out println extractor nextDigit Corresponding output 4 5 0 7 2 Hint use the modulus operator and integer division The modulus operator gives the remainder of dividing two integers For example the result of 17 3 is 2 17 divided by 3 has a remainder of 2 Reminder Integer division is done with the operator performed on two integers For example the result of 17 3 is 5 Do not write your answer here The class interface and space for your answer is provided on the next page 3 Problem 2 cont Complete the implementation of DigitExtractor details of this problem are on the previous page DigitExtractor breaks up a positive integer into its individual digits in reverse order public class DigitExtractor Creates digit extractor for the given integer param anInt the integer to extract from PRE anInt 0 public DigitExtractor int anInt Returns true iff there are more digits left to extract public boolean hasNextDigit Extracts the the next digit in the integer starts from rightmost digit and goes leftward PRE hasNextDigit return the digit public int nextDigit 4 Problem 3 10 pts Implement the static method printAddProblem which takes as its parameter an array of integers and prints out the values as an addition problem When given an array of length 0 it should print nothing See examples below for the exact format to use Ex1 Output of a call to printAddProblem on the array 3 7 2 3 7 2 Ex2 Output of a call to printAddProblem on the array 3 3 Ex3 Output of a call to printAddProblem on the array 3 7 0 2 3 7 0 2 Prints out the given sequence of numbers as an addition problem param nums the numbers to make the addition problem from public static void printAddProblem int nums 5 Problem 4 15 pts total Implement the static method pack which takes out all of the zeroes from an array packing the resulting values to the left This method does not do the packing in place but puts the packed version in another array packed leaving the original array unchanged While the array we start out with has zero and or non zero values throughout the resulting array is a partially filled array which can be described by the array itself 2nd parameter plus an integer size return value which describes which part of the array is being used Note this problem doesn t involve any array resizing In the following examples assume arr length and packed length are 5 although in general they can have any length as long as packed starts out as big as arr The means that the value is unknown i e not significant arr after call to pack arr packed packed return value Ex1 5 0 0 2 4 5 2 4 3 Ex2 0 0 0 0 0 0 Ex3 5 0 0 3 0 5 3 2 Ex4 5 0 0 0 0 5 1 Ex5 0 0 0 0 5 5 1 One more example example but where arr length and packed length are 10 after call to pack arr packed arr Ex6 0 2 3 4 0 6 5 0 0 1 packed return value 2 3 4 6 5 1 6 For full credit your answer must be efficient for example it shouldn t take many steps to do something that can be done in one step Method interface Removes all 0 values from the array packing the resulting values to the left the changed version is in packed original array unchanged param arr The array to pack unchanged by method param packed The resulting packed array PRE packed length arr length return the size of the resulting partially filled array the valid values are now in packed 0 through packed size 1 public static int pack int arr int packed This header and space for your answer is provided on the next page 6 Problem 5 cont Removes all 0 values from the array packing the resulting values to the left the changed version is in packed original array unchanged param arr The array to pack unchanged by method param packed The resulting packed array PRE packed length arr length return the size of the resulting partially filled array the valid values are now in packed 0 through packed size 1 public static int pack int arr int packed 7